Synergistic Effect of Dual Additive System on Molecular Structure and Foaming Properties of Recycled PET

This study investigated the effect of chain extenders on molecular structure and foaming properties of poly (ethylene terephthalate) (PET) bottle flake (BF). To improve the melt strength of BF, two different chain extenders, pyromellitic dianhydride (PMDA) and BASF Joncryl ADR4468, were introduced, and the optimized composition was determined based on the melt viscosity of BF, which resulted in improvements in both the storage modulus and the complex viscosity. The foaming was achieved by applying a chemical blowing agent to the compositions of BF_p and BF_d3 samples which is required for the minimum intrinsic viscosity for the possible chemical foaming process. The formation of small and uniform cells within virgin PET (vPET) and BF was confirmed through the field emission scanning electron microscopy (FE-SEM). The vPET and BF using recipe R3, optimized chain extender composition, was found to be formed the lower density PET foam. In addition, the formation of a long-chain branched (LCB) structure was observed from the rheological behavior, therefore, it could be suggested that a dual additive system successfully proved a synergistic effect in PET foaming performance.